Substrate coating unit and substrate coating method

ABSTRACT

The present invention is a coating unit for applying a coating solution to a substrate which includes: a discharge nozzle for reciprocating in a predetermined direction above the substrate and discharging the coating solution to the substrate; a holder for holding the substrate and horizontally movable in one direction perpendicular to the predetermined direction; and a cover for covering an upper face of the substrate when the substrate is moved in the one direction to be more forward than the discharge nozzle as viewed from a plane, wherein a lower face of the cover is inclined such as to be higher on the discharge nozzle side. According to the present invention, the cover covering the upper face of the substrate restrains a solvent from evaporating from the coating solution applied on the substrate to secure flatness of a coating film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate coating unit and asubstrate coating method.

2. Description of the Related Art

In a photolithography process, for example, in semiconductor devicefabrication processes, a resist coating treatment for applying a resistsolution to a wafer surface to form a resist film thereon, an exposureprocessing for exposing a pattern on the wafer, a developing treatmentfor developing the wafer after the exposure, and so on are performed toform a predetermined circuit pattern on the wafer.

In these days, in the resist coating treatment, a spin coating method isfrequently employed in which the resist solution is discharged onto acenter of a rotated wafer to diffuse the resist solution over the wafersurface.

However, in the spin coating method, the wafer is rotated at a highspeed, which causes a large amount of the resist solution to scatterfrom the peripheral portion of the wafer, resulting in much waste resistsolution. Further, there is a disadvantage that a unit for the coatingis contaminated by the scattered resist solution, and thus the unitneeds to be cleaned frequently, and so on.

Hence, in place of the spin coating method of rotating the wafer, whatcan be proposed is a coating method of applying the resist solution in amanner of so-called drawing with one stroke of discharging the resistsolution from a resist solution discharge part while relatively movingthe wafer and the resist solution discharge part to apply it, forexample, in a rectangular wave form evenly over the wafer. In thiscoating method of so-called drawing with one stroke, for example, theresist solution discharge part discharges the resist solution whilereciprocating in a Y-direction above the wafer and the wafer is moved bya small distance in an X-direction every return of the resist solutiondischarge part to thereby shift a coating position, so that the resistsolution is applied on the entire surface of the wafer.

Meanwhile, in the coating method in a manner of so-called drawing withone stroke, for example, a resist solution with a low viscosity is usedand the resist solution is linearly applied on the wafer. However, theresist solution, if left as it is, heaps up along an application path,and thus the resist solution needs to be diffused over the entire faceof the wafer after the application. Therefore, in order to keep theresist solution having a low viscosity, it becomes necessary to coverthe wafer, for example, with a cover so that a solvent in the resistsolution will not evaporate. Moreover, in order to effectively restrainthe evaporation of the solvent, it is desirable to locate the cover asclose as possible to the wafer.

However, when the cover is provided above the wafer and the wafer ismoved in the X-direction, an air current flowing in the X-direction isformed between the wafer and the cover. Further, since the air currenthas a velocity gradient due to the influence of the cover and a shearingstress is generated on the wafer surface by the velocity gradient, theapplication state of the resist solution immediately after theapplication might be disturbed by the shearing stress. Furthermore, itis also feared that the shearing stress increases as the cover isbrought closer to the wafer to lose the flatness of the resist solution.If the flatness of the resist solution is lost as described above, aresist film having a uniform film thickness is not formed on the wafer,resulting in a decrease in yield.

SUMMARY OF THE INVENTION

The present invention is made in view of the above points, and it is anobject of the present invention to provide a substrate coating unit anda substrate coating method for, when a coating solution such as a resistsolution or the like is applied in a manner of so-called drawing withone stroke, securing flatness of the coating solution while restrainingevaporation of a solvent of the coating solution applied on a substratesuch as a wafer or the like.

In order to attain the above object, a coating unit of the presentinvention comprises: a discharge nozzle for reciprocating in apredetermined direction above the substrate and discharging the coatingsolution to the substrate; a holder for holding the substrate andhorizontally movable in one direction perpendicular to the predetermineddirection; and a cover for covering an upper face of the substrate whenthe substrate is moved in the one direction to be more forward than thedischarge nozzle as viewed from a plane, wherein a lower face of thecover is inclined such as to be higher on the discharge nozzle side.

Further, according to another aspect, a coating unit of the presentinvention comprises: a discharge nozzle for reciprocating in apredetermined direction above the substrate and discharging the coatingsolution to the substrate; a holder for holding the substrate andhorizontally movable in one direction perpendicular to the predetermineddirection; and a cover for covering an upper face of the substrate whenthe substrate is moved in the one direction to be more forward than thedischarge nozzle as viewed from a plane, wherein a lower face of thecover is inclined such as to be lower on the discharge nozzle side.

According to still another aspect, a coating unit of the presentinvention comprises: a discharge nozzle for reciprocating in apredetermined direction above the substrate and discharging the coatingsolution to the substrate; a holder for holding the substrate andhorizontally movable in one direction perpendicular to the predetermineddirection; a cover for covering an upper face of the substrate; and acover moving device for moving the cover in a direction perpendicular tothe predetermined direction.

A coating method of the present invention comprises the steps of: adischarge nozzle applying the coating solution onto the substrate whilemoving in a predetermined direction above the substrate; moving thesubstrate by a predetermined distance in one direction perpendicular tothe predetermined direction when the discharge nozzle reaches an outsideof the substrate; thereafter, the discharge nozzle applying the coatingsolution onto the substrate while moving in an opposite direction to thepredetermined direction above the substrate; moving a cover for coveringan upper face of the substrate in the same one direction as thesubstrate when the substrate is moved in the one direction; and movingthe cover to an original position of the cover before the movement whenthe discharge nozzle applies the coating solution to the substrate whilemoving in the opposite direction to the predetermined direction.

With the coating unit of the present invention, it is possible, first ofall, to conduct the coating method in a manner of so-called drawing withone stroke of relatively moving the substrate and the discharge nozzleto apply the coating solution in a rectangular form evenly over thesubstrate since the coating unit has the discharge nozzle capable ofreciprocating in the predetermined direction above the substrate and theholder for the substrate movable in the one direction perpendicular tothe predetermined direction. Further, the cover covering the upper faceof the substrate restrains the solvent from evaporating from the coatingsolution applied on the substrate to keep a low viscosity of the coatingsolution. Furthermore, since the cover is made higher on the dischargenozzle side, a wide gap is formed between the substrate and the coverwhen the substrate immediately after application is moved in the onedirection. Thereby, when an air current occurs accompanying the movementof the substrate, it is possible to restrain the coating solution frombeing disturbed by the air current, so that the flatness of the coatingsolution is secured accordingly.

As described above, it is feared that when the substrate is moved, thecoating solution on the substrate is drawn backward with respect to thedirection of movement by a shearing stress due to a velocity gradient ofthe air current, resulting in the coating solution on the substratebecoming thinner on the movement direction side. In the presentinvention, however, a wide gap is provided between the substrate and thecover, which restrains a large shearing stress from occurring on thesurface of the substrate immediately after the application to therebyrestrain the coating solution from becoming thinner only on the movementdirection side. Thereby, evenness in thickness of the coating solutionis secured within a substrate plane. Further, since the cover isprovided at an angle, the gap between the substrate and the covernarrows as the substrate advances in the one direction, so thatexcessive evaporation of the solvent in the coating solution can berestrained.

Further, if the cover is lowered on the discharge nozzle side, when thesubstrate immediately after the application is moved in the onedirection, a narrow gap is formed between the substrate and the cover.Then, a shear flow formed in the gap by the movement of the substratecauses a shearing stress on the surface of the coating solution, so thatthe coating solution can be flattened by the shearing stress.Particularly when the coating solution is applied in a manner ofso-called drawing with one stroke, a heap of the coating solution isformed along the application path immediately after the application, butthe coating solution is flattened by the shear flow, resulting inimproved flatness of the coating solution.

The lower face of the aforementioned cover may be curved. By thuscurving the lower face of the cover, an air current between thesubstrate and the cover smoothly flows along the curved face to stablethe behavior of the air current. This stables the coating solution whichis susceptible to the air current, resulting in the formation of anappropriate coating film on the substrate.

In the present invention, it is also preferable that the cover has aflat plate shape with a uniform thickness and a cover raising andlowering mechanism for raising and lowering a part of the cover isprovided. The cover can be raised and lowered by a predetermineddistance to be inclined by the cover raising and lowering mechanism.Further, by adjusting the raising and lowering distance, an inclinedangle of the cover can be adjusted, so that the distance of the gapbetween the substrate and the cover becomes adjustable. Therefore, thedistance is preferably adjusted based on the film thickness, which makesit possible to restrain the evaporation of the solvent from the coatingsolution to a minimum while restraining the influence of the aircurrent.

The cover raising and lowering mechanism may be configured to raise andlower portions in vicinities of both ends along the one direction of thecover. By raising and lowering both ends of the cover, the raising andlowering distance of both ends can be adjusted to adjust the inclinedangle of the cover. Further, since the whole cover can be moved up anddown by raising and lowering both ends of the cover at both sides, thedistance of the gap between the substrate and the cover can be changed.By changing the distance of the gap, the air current formed between thesubstrate and the cover can be controlled. Therefore, it is possible tosecure the flatness of the coating solution while restraining theevaporation of the solvent of the coating solution on the substrate byadjusting the distance of the gap in accordance with the type of thecoating solution, the film thickness, and the moving speed of thesubstrate.

According to the coating method of the present invention, when thesubstrate is shifted in the one direction, the cover is also moved inthe same direction, so that the air current formed between the substrateand the cover by the movement of the substrate decreases in velocitygradient. This reduces the influence of the air current exerted upon thecoating solution on the substrate, so that the behavior of the coatingsolution stables to secure the flatness of the coating solution.Further, the cover is moved to its original position while the dischargenozzle is discharging the coating solution onto the substrate, whichprevents a large amount of solvent from evaporating due to the coverdeviating from a position above the substrate, so that a space formoving the cover is reduced to a minimum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plane view showing a schematic configuration of a coatingand developing treatment system including a resist coating unitaccording to an embodiment;

FIG. 2 is a front view of the coating and developing treatment system inFIG. 1;

FIG. 3 is a rear view of the coating and developing treatment system inFIG. 1;

FIG. 4 is an explanatory view of a vertical cross section showing aconfiguration of the resist coating unit;

FIG. 5 is an explanatory view of a horizontal cross section showing theconfiguration of the resist coating unit;

FIG. 6 is a perspective view showing a configuration of a nozzle movingmechanism;

FIG. 7 is an explanatory view of a horizontal cross section showing theconfiguration of the resist coating unit when an inner container movesto a processing section R side;

FIG. 8 is an explanatory view showing a path of application of a resistsolution;

FIG. 9 is an explanatory view of an outer container schematicallyshowing, from a side, the state where a cover is raised;

FIG. 10 is a graph showing results of an experiment in which a filmthickness of a resist solution on a wafer is measured with a gap betweenthe wafer and the cover changed;

FIG. 11 is a side view schematically showing the inside of the outercontainer when hinge members are attached to the cover;

FIG. 12 is a side view schematically showing the inside of the outercontainer when a cover having another shape is used;

FIG. 13 is an explanatory view schematically showing a configuration ofan outer container in a second embodiment;

FIG. 14 is an explanatory view schematically showing, from a side, theinside of the outer container when raising and lowering drivers areattached to the cover at two points;

FIG. 15 is an explanatory view showing a configuration example of theinside of the outer container when the cover is formed in a curvedshape;

FIG. 16 is an explanatory view of a vertical cross section showing aconfiguration of a resist coating unit in a third embodiment;

FIG. 17 is an explanatory view of a horizontal cross section of theresist coating unit in FIG. 16;

FIG. 18 is a schematic plane view of an outer container for explainingoperations of the resist coating unit in the third embodiment;

FIG. 19 is a schematic plane view of the outer container for explainingthe operations of the resist coating unit in the third embodiment;

FIG. 20 is an explanatory view of an example including an input deviceof a film thickness into a controller; and

FIG. 21 is an explanatory view of a cover having a temperature regulatortherein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will beexplained to detail the present invention. FIG. 1 is a schematic planeview of a coating and developing treatment system 1 including asubstrate coating unit according to an embodiment, FIG. 2 is a frontview of the coating and developing treatment system 1, and FIG. 3 is arear view of the coating and developing treatment system 1.

As shown in FIG. 1, the coating and developing treatment system 1 has aconfiguration in which a cassette station 2 for carrying, for example,25 wafers W in a unit of cassette from/to the outside to/from thecoating and developing treatment system 1 and for carrying the wafers Wto/from a cassette C, a processing station 3 composed of various kindsof processing units which are disposed in multi-tiers, for performingpredetermined processing for the wafers W one by one in coating anddeveloping processes, and an interface section 4 fordelivering/receiving the wafers W to/from a not-shown aligner which isprovided adjacent to the processing station 3 are integrally connected.

In the cassette station 2, a plurality of the cassettes C are mountablein predetermined positions on a cassette mounting table 5, which servesas a mounting portion, in a line in an X-direction (a vertical directionin FIG. 1). Furthermore, a wafer carrier 7, which is transportable inthe alignment direction of the cassettes (the X-direction) and in analignment direction of the wafers W housed in the cassette C (aZ-direction; a vertical direction), is provided to be movable along acarrier path 8 so that it can selectively access to each of thecassettes C.

The wafer carrier 7 has an alignment function for aligning the wafers W.The wafer carrier 7 is also configured to be able to access to anextension unit 32 included in a third processing unit group G3 on theprocessing station 3 side as will be described below.

In the processing station 3, a main carrier 13 is provided in a centerpart thereof, and various kinds of the processing units are multi-tieredon a periphery of the main carrier 13 to constitute processing unitgroups. In the coating and developing treatment system 1, where fourprocessing unit groups G1, G2, G3 and G4 are arranged, the first andsecond processing unit groups G1 and G2 are disposed on a front side ofthe coating and developing treatment system 1, the third processing unitgroup G3 is disposed adjacent to the cassette station 2, and the fourthprocessing unit group G4 is disposed adjacent to the interface section4. Furthermore, a fifth processing unit group G5 depicted by a brokenline is allowed to be additionally disposed on a rear side as an option.The main carrier 13 is capable of carrying the wafers W to/from thelater described various kinds of processing units which are disposed inthese processing unit groups G1, G2, G3, G4 and G5. Incidentally, thenumber and the arrangement of the processing unit groups vary dependingon the kind of processing performed on the wafers W, and the number ofthe processing unit groups is arbitrarily selected if it is one or more.

In the first processing unit group G1, for example, as shown in FIG. 2,a resist coating unit 17 as a coating unit according to the presentinvention and a developing unit 18 for developing the wafer W afterexposure are two-tiered in the order from the bottom. Similarly, in theprocessing unit group G2, a resist coating unit 19 and a developing unit20 are two-tiered in the order from the bottom.

In the third processing unit group G3, for example, as shown in FIG. 3,a cooling unit 30 for cooling the wafer W, an adhesion unit 31 forenhancing adhesion between a resist solution and the wafer W, theextension unit 32 for delivering/receiving the wafer W, pre-baking units33 and 34 for evaporating a solvent in the resist solution, and apost-baking unit 35 for performing a heat treatment after a developingtreatment are, for example, six-tiered in the order from the bottom.

In the fourth processing unit group G4, for example, a cooling unit 40,an extension and cooling unit 41 for spontaneously cooling the wafer Wmounted thereon, an extension unit 42, a cooling unit 43, post-exposurebaking units 44 and 45 each for performing a heat treatment afterexposure, and a post-baking unit 46 for performing a heat treatmentafter a developing treatment are, for example, seven-tiered in the orderfrom the bottom.

In a center part of the interface section 4, a wafer carrier 50 isprovided. The wafer carrier 50 is configured to be freely movable in theX-direction (the vertical direction in FIG. 1) and the Z-direction (theperpendicular direction), and to be freely rotatable in a O-direction (adirection of rotation about the Z-axis), so that it can access to theextension and cooling unit 41 and the extension unit 42 included in thefourth processing unit group G4, an edge exposure unit 51, and thenot-shown aligner to carry the wafer W to each of them.

Next, a configuration of the above-described resist coating unit 17 isexplained. FIG. 4 is an explanatory view of a vertical cross sectionshowing a schematic configuration of the resist coating unit 17, andFIG. 5 is an explanatory view of a horizontal cross section showing theschematic configuration of the resist coating unit 17.

In a casing 60 of the resist coating unit 17, as shown in FIG. 4 andFIG. 5, an outer container 61 is provided which is formed in asubstantially box shape elongated in the X-direction (the verticaldirection in FIG. 5) with the upper face open. The outer container 61has a carriage section L where the wafer W is carried in/out and aprocessing section R where coating of the wafer W is performed. Theprocessing section R is located on a positive direction side in theX-direction and the carriage section L is located on a negativedirection side in the X-direction.

In the outer container 61, an inner container 62 is provided which isformed in a substantially box shape with the upper face open andaccommodates the wafer W. In a center part of the inner container 62, aholder 63 for holding the wafer W by sucking it is provided. Under theholder 63, a driver 64 provided with a motor, a cylinder, and so on isprovided to enable the holder 63 to ascend and descend. Thereby, theholder 63 can ascend and descend when the wafer W is carried in andreceive the wafer W preferably from the main carrier 13. Further, theholder 63 is rotatable by the driver 64 so as to rotate the wafer W heldby the holder 63 for alignment. For example, an ultrasonic vibrator 65is attached to the holder 63 and can vibrate the holder 63 at a highfrequency to even the resist solution applied on the wafer W byvibration. At the inner bottom of the inner container 62, solvent tanks66 are provided which store a solvent for the resist solution. Thismakes it possible to keep the inside of the inner container 62 in asolvent atmosphere.

At the inner bottom of the outer container 61, rails 68 are providedwhich extend in the longitudinal direction (the X-direction), and theinner container 62 is provided on the rails 68 to be freely movable. Therails 68 are provided with an inner container moving mechanism 69 formaking the inner container 62 movable. The inner container movingmechanism 69 is constituted by an inner container driver 70 providedwith a motor or the like for moving the inner container 62 by electricpower, a power supply 71 for supplying electric power to the innercontainer driver 70, and an inner container controller 72 for adjustingthe power supply to control the inner container driver 70. Thereby, theinner container 62 becomes movable between the carriage section L andthe processing section R along the rails 68. Further, since the innercontainer 62 can move a predetermined distance at a predetermined timingduring the application, the holder 63 in the inner container 62,accompanying the movement, becomes horizontally movable intermittentlytoward the positive direction side in the X-direction as one direction.

As shown in FIG. 5, a mask member 73 for covering the wafer W during theapplication to limit a coating range of the wafer W is kept waiting, forexample, in a not shown cleaning section located outside the outercontainer 61 on the negative direction side in the X-direction. The maskmember 73 has a flat plate shape having an opening 73 a corresponding tothe coating range at the center part thereof.

The mask member 73 is configured to be movable by a not shown carrier toa position above the wafer W in the inner container 62. Inner walls ofthe inner container 62 are provided with mask supporting members 74 forsupporting the mask member 73 at a position above the wafer W. Thisconfiguration makes it possible to carry the mask member 73 kept waitingin the not shown cleaning section into the inner container 62 after thewafer W is held by the holder 63 and to mount the mask member 73 on themask supporting members 74 above the wafer W. Thereby, a resist solutiondischarged from above by a discharge nozzle 85 as a later-describeddischarge nozzle can be applied only to a predetermined range of thewafer W, and the resist solution which is discharged to the outside ofthe range can be blocked by the mask member 73 and collected.

On the processing section R side of the outer container 61, covers 75and 76 are provided, as shown in FIG. 5, each in a plate shape forcovering the upper face of the wafer W during the application. Each ofthe covers 75 and 76 is formed in a quadrangle as viewed from a plane tofit the shape of the opening of the outer container 61. The cover 75 andthe cover 76 are provided, side by side, on the positive direction sidein the X-direction and on the negative direction side in theX-direction, respectively. Between the covers 75 and 76, a gap d isprovided so that the later-described discharge nozzle 85 can reciprocatein the Y-direction within the gap d and discharge the resist solution tothe wafer W located thereunder. Further, the covers 75 and 76 areprovided such that there is little or no gap with respect to the upperend of the inner container 62, so that when the inner container 62 islocated under the inner the covers 75 and 76, the inside of the innercontainer 62 can be maintained in a predetermined atmosphere. In thisembodiment, the cover 75 corresponds to a cover according to the presentinvention.

The cover 75 is supported by supporting members 77 and 78 which areprovided on inner walls of the outer container 61. The supportingmembers 77 are disposed on the negative direction side in theX-direction of the cover 75, and the supporting members 78 are disposedon the positive direction side in the X-direction of the cover 75.

The cover 75 is configured to be freely ascendable and descendable by acover raising and lowering mechanism 80 as shown in FIG. 4. The coverraising and lowering mechanism 80 has raising and lowering drivers 81each including a cylinder or the like for raising and lowering thesupporting member 77, and a controller 82 for controlling actions of theraising and lowering drivers 81. The raising and lowering drivers 81support lower parts of the supporting members 77 and can move thesupporting members 77 in the vertical direction. This allows thesupporting members 77 to ascend by a predetermined distance to therebyincline the cover 75 to be higher on the negative direction side in theX-direction.

The aforementioned discharge nozzle 85 is provided to be located withinthe gap d. The discharge nozzle 85 is configured to be movable in theY-direction by a nozzle moving mechanism 86 which is provided on thecover 76 of the outer container 61.

The nozzle moving mechanism 86 is covered with a case 86 a as shown inFIG. 6, and a slider 87 for holding and sliding the discharge nozzle 85is provided in the case 86 a. The slider 87 is provided fixed to a partof a driving belt 88 extending in the Y-direction. Further, the drivingbelt 88 is looped between a driving pulley 89 and a driven pulley 90which are provided on both sides in the Y-direction of the outercontainer 61, respectively. The driving pulley 89 is normally/reverselyrotated by a rotation drive motor 91. This configuration makes itpossible that the rotation drive motor 91 rotates the driving pulley 89to move the driving belt 88, which causes the slider 87 to slide in theY-direction, thereby allowing the discharge nozzle 85 to reciprocatewithin the gap d.

The driving belt 88 is provided with, on the side where the dischargenozzle 85 is not held, a balance weight 92 which balances with theslider 87 in weight to restrain, to a minimum, a swing occurring duringthe movement of the slide 87.

According to the above configuration, the discharge nozzle 85 above thewafer W discharges the resist solution onto the wafer W whilereciprocating in the Y-direction, and the inner container 62intermittently moves in the positive direction of the X-direction, sothat the resist solution can be applied to the surface of the wafer W ina manner of so-called drawing with one stroke.

Next, operations of the resist coating unit 17 configured as above areexplained together with steps of a photolithography process which areperformed in the coating and developing treatment system 1.

First of all, the wafer carrier 7 takes out one unprocessed wafer W fromthe cassette C and carries it to the extension unit 32 which is includedin the third processing unit group G3. Then, the wafer W is carried bythe main carrier 13 into the adhesion unit 31, where, for example, HMDSfor enhancing adhesion to the resist solution is applied onto the waferW. The wafer W is then carried to the cooling unit 30 and cooled to apredetermined temperature. The wafer W which has been cooled to thepredetermined temperature is carried to, for example, the resist coatingunit 17 by the main carrier 13.

The wafer W coated with the resist solution in the resist coating unit17 is carried to the pre-baking unit 33 where the wafer W is heattreated. Subsequently, the wafer W is carried to the extension andcooling unit 41 and cooled. Then, the wafer W is taken out of theextension and cooling unit 41 by the wafer carrier 50 and thereaftercarried via the edge exposure unit 51 to the aligner (not shown) where apredetermined pattern is exposed on the wafer W. The wafer W for whichthe exposure processing has been finished is carrier to the extensionunit 42 by the wafer carrier 50 and then carried to the post-exposurebaking unit 44 by the main carrier 13. The wafer W is heat treated andthen carried to the cooling unit 43 where it is subjected to a coolingtreatment.

The wafer W for which the cooling treatment has been finished is carriedto the developing unit 18 by the main carrier 13 and subjected to adeveloping treatment. Thereafter, the wafer W is carried to thepost-baking unit 46 and the cooling unit 30 in sequence to undergopredetermined processing in each unit. Then, the wafer W is returned tothe cassette C via the extension unit 32, whereby a series of coatingand developing processes is finished.

Next, the above-described operations of the resist coating unit 17 areexplained in detail. First of all, when the wafer W is carried to theresist coating unit 17, the inner container 62 is waiting at thecarriage section L on the negative direction side in the X-direction.Then, the wafer W for which the pre-process has been completed iscarried into the inner container 62 by the main carrier 13 and deliveredto the holder 63 which has been raised and is waiting in advance. Thewafer W delivered to the holder 63 is suction held by the holder 63 andlowered to a predetermined height by the driver 64. The wafer W in thisevent is located such that, for example, when the wafer W is moved tothe processing section R side, gaps between the wafer W and the covers75 and 76 are about 4 mm.

Thereafter, a not shown alignment mechanism detects a notch or anorientation flat of the wafer W, and based on the detection the holder63 is rotated to position the wafer W at a predetermined position. Then,the mask member 73 which is kept waiting at the not shown cleaningsection is carried from outside the outer container 61 into the innercontainer 62 and mounted on the mask supporting members 74. In thisevent, the inner container 62 is in a state of being covered with themask member 73, so that the solvent atmosphere in the inner container 62is maintained also by the mask member 73. Subsequently, as shown in FIG.7, the inner container 62 is moved in the positive direction of theX-direction by the inner container moving mechanism 69 and stopped at aposition where an end portion of the wafer W on the positive directionside in the X-direction is positioned under the discharge nozzle 85.

Then, the discharge nozzle 85 is moved by the nozzle driving mechanism86 to a start position S where application is started, that is, aposition outside the wafer W on the negative direction side in theY-direction as shown in FIG. 8. In this event, as shown in FIG. 9, thesupporting members 77 which are located on the discharge nozzle 85 sideof the cover 75 are raised by the raising and lowering drivers 81, whichcauses the cover 75 to incline, so as to widen the gap between the cover75 on the discharge nozzle side 85 and the wafer W.

Subsequently, application of the resist solution is started in a mannerof so-called drawing with one stroke. A resist coating step in this caseis explained with reference to FIG. 8. First, the discharge nozzle 85discharges a linear resist solution to the surface of the wafer W whilemoving in the positive direction of the Y-direction from the startposition S at a predetermined speed. Then, the discharge nozzle 85advances to the outside of the wafer W on the positive direction side inthe Y-direction and once stops above the mask member 73. The resistsolution is kept discharged in this event, and a resist solutiondischarged to a place other than the wafer W is received by the maskmember 73 and collected.

Subsequently, the inner container 62 is shifted in the positivedirection of the X-direction by a predetermined distance by the innercontainer moving mechanism 69, so that the wafer W is also shifted inthe positive direction of the X-direction. In this event, accompanyingthe movement of the wafer W, an air current flowing in the positivedirection of the X-direction is formed in the gap between the wafer Wand the cover 75. However, since the gap of, for example, 4 mm or moreis provided between the wafer W and the cover 75 and further the widergap is provided on the discharge nozzle 85 side, influence by the aircurrent is restrained to a minimum.

Thereafter, the discharge nozzle 85 returns and moves in the negativedirection of the Y-direction while continuously applying the resistsolution, and advances to the outside of the wafer W and stops. Then,the wafer W is shifted by a predetermined distance in the positivedirection of the X-direction, and the discharge nozzle 85 again returnsand advances in the positive direction of the Y-direction to dischargethe resist solution onto the wafer W.

After the above steps are repeated, when the discharge nozzle 85 reachesan END position E shown in FIG. 8, the discharge of the resist solutionis stopped, whereby the resist coating is completed. Thereby, the resistsolution is applied on the wafer W in a rectangular wave form, theresist solution being applied on the entire surface of the wafer W.

Subsequently, the ultrasonic vibrator 65 which is attached to the holder63 vibrates the wafer W to even and flatten the resist solution on thewafer W.

Thereafter, the inner container 62 is moved to the carriage section Lside, and the mask member 73 is carried out from the inside of the outercontainer 61. Then, the wafer W is delivered from the holder 63 in theinner container 62 to the main carrier 13, and the wafer W is carriedout of the resist coating unit 17, whereby a series of processes in theresist coating unit 17 is completed.

An experiment by the inventor confirms that the film thickness of theresist solution applied on the wafer W becomes more even by providing awidened gap of 4 mm (a line a) between the wafer W and the cover 75 thanby providing a gap of 1 mm (a line b) as shown in FIG. 10. Morespecifically, when the gap between the wafer W and the cover 75 is made4 mm or more, the resist solution applied on the wafer W becomesunsusceptible to the air current occurring in the gap, so that theflatness of the resist solution is secured. In the above embodiment, thegap between the wafer W and the cover 75 is made 4 mm or more, so thatthe influence by the air current in the gap occurring when the wafer Wis moved in the positive direction of the X-direction is restrained tosecure the flatness of the resist solution.

The resist solution immediately after the application has the lowestviscosity because the solvent therein has not evaporated, and thus it issusceptible to the air current and so on. In the above embodiment, thecover 75 on the discharge nozzle 85 side is raised to incline by thecover raising and lowering mechanism 80. Thus, when the wafer Wimmediately after the application is moved in the X-direction to facethe cover 75 for the first time, the gap between the wafer W and thecover 75 is the largest, so that the influence by the air current isrestrained to a minimum. Further, since the cover 75 is lowered on thepositive direction side in the X-direction where there is littleinfluence exerted upon the resist solution on the wafer W, the gap isnarrowed to restrain evaporation of the solvent from the resistsolution.

Furthermore, since the inclination of the cover 75 can be adjusted bythe cover raising and lowering mechanism 80, it is possible to adjustthe width or narrowness of the gap between the cover 75 on the dischargenozzle 85 side and the wafer W. This makes it possible to adjust the gapso as to restrain the influence by the air current while evaporation ofthe solvent is being restrained. Moreover, it is possible to change thegap as required in accordance with the type of the resist solution, thesize of the wafer W, and so on.

While the positive direction side in the X-direction of the cover 75 issupported by the supporting members 78 in the above embodiment, it isalso adoptable to attach hinge members 100 to ends of the cover 75 onthe positive direction side in the X-direction as shown in FIG. 11. Thisenables the cover 75 to pivot about the end parts of the cover 75, sothat the inclination action of the cover 75 is preferably performed.

It should be noted that, to incline the cover 75, it is also adoptableto provide the cover 75 at an angle in advance, or to use a cover 105having a shape with a lower face inclined as shown in FIG. 12.

Moreover, it is preferable that the surface of the lower face of thecover 75 is smooth without projections and depressions. This is becauseoccurrence of a turbulent flow can be prevented further.

While the cover 75 is inclined such that the cover 75 is higher on thedischarge nozzle 85 side in the above embodiment, the cover 75 may beinclined such that it is lower on the discharge nozzle 85 side. Thiscase is explained as a second embodiment. For example, as shown in FIG.13, a cover 111 in a flat plate shape is provided on the positivedirection side in the X-direction with respect to a discharge nozzle 110as in the first embodiment. The cover 111 is provided such that when thewafer W is moved to a position under the cover 111, a gap between thecover 111 and the wafer W is 4 mm. The cover 111 is supported bysupporting members 112 and 113, and the supporting members 112 whichsupport the negative direction side in the X-direction of the cover 111are provided with a cover raising and lowering mechanism 114 forlowering the supporting members 112. The cover raising and loweringmechanism 114 is constituted by raising and lowering drivers 115 forsupporting the supporting members 112 and freely moving up and down thesupporting members 112, and a controller 116 for controlling the raisingand lowering drivers 115. Incidentally, the configuration of the otherpart is the same as that of the first embodiment, and thus theexplanation thereof is omitted.

In the coating treatment of the resist solution, the supporting members112 are lowered by a predetermined distance by the cover raising andlowering mechanism 114 before the start of application to incline thecover 111 so that the cover 111 is lower on the discharge nozzle 110side. In this event, a gap between the cover 111 and the wafer W is setsuch that when the wafer W is moved to a position under the cover 111,the gap is about 1 mm on the discharge nozzle 110 side. Thereafter, whenthe resist solution is applied to the wafer W and the wafer W advancesin the positive direction of the X-direction, the wafer W is locatedunder the cover 111 to form a gap of 4 mm between the wafer W and thecover 111. Then, when the wafer W is intermittently moved in thepositive direction of the X-direction, an air current having a velocitygradient is formed in the gap. Due to the velocity gradient of the aircurrent, a shearing stress acts on the surface of the resist solution.Then, the shearing stress flattens the resist solution immediately afterthe application.

As described above, according to the second embodiment, the gap betweenthe wafer W and the cover 111 is positively narrowed so that the resistsolution on the wafer W is evened by the shearing stress caused by theair current in the gap to secure the flatness of the resist solution.

While the raising and lowering drivers for raising and lowering thecover are provided only at the supporting members on the dischargenozzle side in the above embodiment, the raising and lowering driversmay be provided at the supporting members on the positive direction sidein the X-direction. For example, the cover raising and loweringmechanism 80 is designed to have raising and lowering drivers 120 forsupporting and moving up and down the supporting members 78, and acontroller 121 for controlling the raising and lowering drivers 120 asshown in FIG. 14. Further, for example, the supporting members 77 andthe supporting members 78 are raised by predetermined distances beforethe application to incline the cover 75 such that the cover 75 becomeshigher on the discharge nozzle 85 side. Thereby, the air current formedbetween the wafer W and the cover 75 is controlled as in the firstembodiment, so that the flatness of the resist solution is secured.

Moreover, in this case, by raising and lowering the supporting members77 and the supporting members 78 by predetermined distances, the heightof the whole cover 75 can also be adjusted. For example, while thesupporting members 78 are located to form the gap of 4 mm with the waferW in the first embodiment, the gap may be made 4 mm or more, or 4 mm orless in comparative consideration of the flatness of the resist solutionand the amount of solvent evaporation. This makes it possible to providea more appropriate gap between the wafer W and the cover 75. Further,the timing of changing the height of the whole cover 75 may be providedduring the application of the resist solution. Since, during theapplication, the cover 75 is inclined and the wafer W is moved, anoptimal gap always changes. By changing the gap during the application,the air current in the gap can be controlled more precisely so as torestrain turbulence of the resist solution to a minimum. Incidentally,the above-described case in which the cover is raised and lowered at twopoints is also applicable to the second embodiment.

While the cover described in the above embodiments is in a flat plateshape, a cover 125 may be curved protruding downward as shown in FIG.15. In this case, an air current occurring between the wafer W and thecover 125 smoothly flows to form into a stable air current. Thisrestrains the resist solution on the wafer W from being disturbed by theair current so as to secure the flatness of the resist solution.Incidentally, the cover 125 may be in a curved shape protruding upward.

Next, a cover moving device may be provided which can move the cover 75in the X-direction and control the movement of the cover 75.Hereinafter, this case is explained as a third embodiment.

A resist coating unit 130 in the third embodiment is provided with, forexample, rails 132 extending in the X-direction on inner walls of theprocessing section R side of an outer container 131 as shown in FIG. 16and FIG. 17. A cover 133 in a flat plate shape is provided to be freelymovable along the rails 132. The rail 132 is provided with a coverdriver 134 including a motor or the like for moving the cover 133 alongthe rail 132, and the movement of the cover driver 134 is controlled bythe inner container controller 72 for controlling the movement of theinner container 62. The inner container controller 72 can move the innercontainer 62 and the cover 133 synchronously or individually. Asdescribed above, the cover moving device is constituted, for example, bythe rails 132, the cover drivers 134, and the inner container controller72. Incidentally, the configuration of the other part is the same asthat of the above-described embodiments, and thus the explanationthereof is omitted.

Next, operations of the resist coating unit 130 of the third embodimentare explained. A wafer W carried in the resist coating unit 130 is heldby the holder 63 in the inner container 62 and moved to a position,where application is started, by the movement of the inner container 62.Then, when the application of the resist solution is started, thedischarge nozzle 85 first moves in the positive direction of theY-direction from the start position S and discharges the resist solutiononto the wafer W. When the discharge nozzle 85 reaches the outside ofthe wafer W on the negative direction side in the Y-direction, thedischarge nozzle 85 is once stopped there.

Then, the inner container 62 moves by a predetermined distance in thepositive direction of the X-direction, whereby a coating position of thewafer W is shifted. In this event, the cover 133 is moved in thepositive direction of the X-direction by the same distance as that ofthe inner container 62 in synchronization therewith as shown in FIG. 18.Subsequently, the discharge nozzle 85 moves in the negative direction ofthe Y-direction and discharges the resist solution onto the wafer W. Inthis event, as shown in FIG. 19, the cover 133 is returned to itsoriginal position slowly, for example, at a speed lower than that whenit moves in the positive direction of the X-direction.

When the discharge nozzle 85 reaches the outside of the wafer W, thedischarge nozzle 85 is stopped, and the inner container 62 is moved by apredetermined distance in the positive direction of the X-direction tobe shifted. In this event, the cover 133 is also moved in the positivedirection of the X-direction in synchronization with the wafer W as inthe aforesaid case. Then, when the discharge nozzle 85 again moves inthe positive direction of the Y-direction, the cover 133 is returned tothe original position.

As described above, when the inner container 62 shifts in the positivedirection of the X-direction, the cover 133 is designed to similarlymove in the positive direction of the X-direction, and thereafter thecover 133 is designed to return to the original position while thedischarge nozzle 85 is moving in the Y-direction and discharging theresist solution. This makes it possible to decrease the velocitygradient of an air current formed between the wafer W and the cover 133when the wafer W is moved in the positive direction of the X-directionso as to decrease a shearing stress exerted upon the surface of theresist solution. Further, since the cover 133 is slowly returned to theoriginal position while the discharge nozzle 85 is moving in theY-direction, the solvent in the resist solution can be restrained fromevaporating from the wafer W due to a widened gap d. Furthermore, thecover 133 is returned at a low speed, which prevents an air currenthaving a large velocity gradient from being formed by the movement inreturning, and exerting adverse influence upon the resist solution.

Meanwhile, the coating solution such as the resist solution applied onthe wafer W moves more easily as its film thickness increases. Further,as the cover 75 is located closer to the wafer W, the cover 75 canrestrain more greatly the evaporation of the solution on the wafer W torestrain occurrence of turbulence increasingly. Thus, it is preferableto keep more distance between the cover 75 and the surface of the waferW the larger the film thickness is, and to keep the cover 75 closer tothe surface of wafer W the smaller the film thickness is.

Therefore, a degree of moving up and down the supporting members 77 isinputted in advance into the controller 82 for controlling the actionsof the raising and lowering drivers 81 based on a film thickness to beapplied on the surface of the wafer W, which makes it possible topreferably control a degree of approaching/retracting of the cover 75to/from the surface of the wafer W based on the film thickness.

In this case, as shown in FIG. 20, an input device 140 for inputting thefilm thickness into the controller 82 is connected to the controller 82,while the controller 82 is provided with a memory storing, in advance,the relationship between a film thickness and a preferable degree ofapproaching/retracting of the cover to/from the wafer W corresponding tothe film thickness. The above configuration is employed, so that, basedon film thickness information inputted from the input device 140, thecontroller 82 selects an optimal degree of approaching/retracting of thecover 75 corresponding to the film thickness registered in the memory,and outputs it to the raising and lowering drivers 81. Based on this,the raising and lowering drivers 81 cause the cover 75 to approach andretract. This is also effective in the examples shown in FIGS. 11, 13,and 14.

Meanwhile, evaporation from the coating film such as a resist film orthe like applied on the wafer W is influenced by temperature. Regardingthis point, for example, a temperature regulator 141 may be accommodatedinside the cover 75 as shown in FIG. 21 to control the temperature ofthe cover 75, particularly the temperature of the lower face of thecover 75.

The temperature regulator 141 itself can employ a well-known techniquesuch as a flow passage through which, for example, a cooling waterflows, a Peltier element, a heat pipe, or the like.

Further, a range of temperature control is preferably, for example, from10° C. to 23° C. This is because a temperature below 10° C. might causecondensation on the surface of the cover 75, and a temperature above 23°C. might contrarily promote evaporation from the applied solution. Thus,the temperature of the cover 75 is controlled in the aforementionedrange, which can restrain evaporation from the coating film on thesurface of the wafer W, resulting in restraint of occurrence of an aircurrent.

As for the material of the cover 75, a material having good heatconductivity is suitable such as stainless steel, aluminum, or the like,but resin or silica glass is not so suitable.

It should be noted that as for the cover 76 covering the wafer W, atemperature regulator 142 may be accommodated therein in the samemanner.

The above-described embodiments are applied to the coating unit forapplying the resist solution onto the wafer, and the present inventionis also applicable to a coating unit for applying another coatingsolution to form an insulating film or the like, for example, a coatingunit for forming an SOD or SOG film or the like. Furthermore, theabove-described embodiments are applied to the coating unit in thephotolithography process of the semiconductor wafer device fabricationprocesses, and the present invention can also be applied to a coatingunit for a substrate other than the semiconductor wafer, for example, anLCD substrate.

According to the present invention, since the flatness of a coatingsolution can be secured by controlling an air current occurring betweena substrate and a cover, a uniform coating film having a predeterminedthickness is formed on the substrate, resulting in improved yield.

1-22. (canceled).
 23. A substrate coating method for applying a coatingsolution to an entire surface of a substrate, comprising the steps of: adischarge nozzle applying the coating solution onto the substrate whilemoving in a predetermined direction above the substrate; moving thesubstrate by a predetermined distance in one direction perpendicular tothe predetermined direction when the discharge nozzle reaches an outsideof the substrate; thereafter, the discharge nozzle applying the coatingsolution onto the substrate while moving in an opposite direction to thepredetermined direction above the substrate; moving a cover for coveringan upper face of the substrate in the same one direction as thesubstrate when the substrate is moved in the one direction; and movingthe cover to an original position of the cover before the movement whenthe discharge nozzle applies the coating solution to the substrate whilemoving in the opposite direction to the predetermined direction.
 24. Asubstrate coating method as set forth in claim 23, wherein a speed whenthe cover moves to the original position is lower than a speed when thecover moves in the one direction by a predetermined distance. 25.(canceled).
 26. A substrate coating method as set forth in claim 23,wherein said lower face of said cover is curved.
 27. A substrate coatingmethod as set forth in claim 23, wherein a temperature of said cover isadjustable.
 28. A substrate coating method as set forth in claim 23,wherein a temperature of said cover is adjusted in a range of 10° C. to23° C.
 29. A substrate coating method as set forth in claim 23, whereina flow passage for a cooling water is formed in said cover.
 30. Asubstrate coating method as set forth in claim 23, wherein a Peltierelement is accommodated in said cover.
 31. A substrate coating method asset forth in claim 23, wherein a heat pipe device is accommodated insaid cover.
 32. A substrate coating method as set forth in claim 23,wherein a surface of said lower face of said cover is smooth withoutprojections and depressions.